Coronary artery disease remains the leading cause of morbidity and mortality in Western societies and is manifested in a number of ways. For example, disease of the coronary arteries can lead to insufficient blood flow to various areas of the heart. This can lead to the discomfort of angina and the risk of ischemia. In severe cases, acute blockage of coronary blood flow can result in irreversible damage to the myocardial tissue, including myocardial infarction and the risk of death.
A number of approaches have been developed for treating coronary artery disease. In less severe cases, it is often sufficient to merely treat the symptoms, with pharmaceuticals, or treat the underlying causes of the disease, with lifestyle modification. In more severe cases, the coronary blockage can be treated endovascularly or percutaneously using techniques such as balloon angioplasty, atherectomy, laser ablation, stents, and the like.
In cases where these approaches have failed or are likely to fail, it is often necessary to perform a coronary artery bypass graft procedure. This procedure generally involves opening the chest by median sternotomy, spreading the left and right rib cage apart; and opening the pericardial sac to achieve direct access to the heart. Next, a blood vessel or vessels for use in the graft procedure are mobilized from the patient. This usually entails mobilizing either a mammary artery or a saphenous vein, although other graft vessels may also be used.
Commonly, a heart-lung or cardiopulmonary bypass is performed so that the beating of the heart can be stopped during the surgical procedure. This usually entails arterial and venous cannulation, connecting the bloodstream to a heart-lung machine, cooling the body to about 32 degrees Celsius, cross-clamping of the aorta and cardioplegic perfusion of the coronary arteries to arrest and cool the heart to about 4 degrees Celsius. The arrest or stoppage of the heart is generally required because the constant pumping motion of the beating heart would make surgery upon the heart difficult in some locations and extremely difficult if not impossible in other locations
Once cardiac arrest is achieved, a graft (or grafts) is attached to the relevant portions of a coronary artery (or arteries) followed by weaning from the cardiopulmonary bypass, restarting the heart, and decannulation. Finally the chest is closed.
However, use of the cardiopulmonary bypass may create difficulties for the patient and increase the expense and time required for the procedure. In a cardiopulmonary bypass, all the patient's blood, which normally returns to the right atrium, is diverted to a system which supplies oxygen to the blood, removes carbon dioxide, and returns the blood, at sufficient pressure, into the patient's aorta for further distribution into the body. Generally, such a system requires several separate components, including an oxygenator, several pumps, a reservoir, a blood temperature control system, filters, and flow, pressure, and temperature sensors.
Due to the risks incurred during cardiopulmonary bypass, others have attempted to perform a coronary artery bypass graft procedure without cardiac arrest and cardiopulmonary bypass in a procedure known as an "off pump coronary artery bypass" (OPCAB) procedure. For example, Trapp and Bisarya (Annals Thorac. Surg. 19(1):1-9, 1975) immobilized the area of the bypass graft by encircling sutures deep enough to incorporate enough muscle to suspend an area of the heart while preventing damage to the coronary artery. More recently, Fanning et al (Annals Thorac. Surg. 55: 486-489, 1993) reported immobilizing the area of the bypass graft with stabilization sutures.
While these attempts have achieved some success, they generally require enhanced skill of the surgeon to properly create the anastomosis because, even with use of sutures to suspend a portion of the surface of the heart upon which the surgery is conducted, the beating heart continues to move more than desired in the relevant area. In addition, the sutures may cause a myocardial tear, an injury of the coronary artery branches, or such complications as embolism or focal arteriosclerosis resulting from the pressures of the ligatures upon the artery.
In order to solve such problems associated with the use of sutures to stabilize the site of an anastomosis upon the surface of a beating heart, a device known as a "local myocardial compression device" has been developed wherein myocardial portions on both sides of the coronary artery on which anastomosis is to be performed are compressed with a two-tined fork-like instrument to apply pressure upon the artery and the heart itself so as to stabilize the treatment site. While use of this device has met with some success, the application of local compression to the heart can effect considerable local deterioration of cardiac function, particularly when cardiopulmonary bypass is not used to supplement blood circulation. In addition, this device does not address the problem of bleeding from a locally dissected coronary artery intended for anastomosis.
To address the undesirable effect of compression of the heart, such as is caused by use of the local myocardial compression device, a suction-assisted device has been developed. The suction-assisted device has two paddles, each of which includes a series of suction ports located at the point where the device interfaces with the surface of the heart, as described in U.S. Pat. No. 5,836,311. The paddles are applied to the surface of the heart across an arterial section intended as an anastomotic site and suction applied through the suction ports is employed to lift and hold the surface tissue of a beating heart at the anastomotic site to minimize motion of the treatment site while the heart continues to beat underneath. This device may be used in either a conventional, open-chest environment or in an endoscopic minimally invasive procedure. However, it has been discovered that application of pressure at localized points using such a device can cause suction induced hemorrhages on the surface of the heart that result in scarring of the heart.
The need for stabilization of a moveable surgical or biopsy site (i.e., a treatment site) is not limited to the case of the beating heart. Robotic surgery is presently being conducted on a number of internal organs. Such surgeries would be enhanced by a stabilizing device that could be inserted through a small surgically created opening to control the movement or otherwise stabilize the surgical site to aid in visualization and manipulation of the surgical site remotely, i.e., during robotic surgery.
A number of minimally invasive surgical (MIS) techniques have been developed to minimize both the time required for surgery or diagnosis and the size of the surgical opening created in the patient's body. To perform MIS, the surgeon uses special instruments that allow the surgeon to maneuver inside the patient. One type of instrument that is used in minimally invasive surgery is forceps, an instrument having a tip specifically configured to grasp objects, such as needles. Because forceps and other instruments designed for minimally invasive surgery are generally long and rigid, they may fail to provide a surgeon the dexterity and precision necessary to effectively carry out many procedures in a minimally invasive fashion that requiring extensive delicate suturing. This problem is increased if the surgical site is in motion during MIS due its anatomical location, such as the surface of a beating heart.
Robotic systems for use in surgery are being developed to increase a surgeon's dexterity as well as to allow a surgeon to operate on a patient from a remote location. In these robotic systems, the surgeon uses some form of servomechanism, usually computer driven, to manipulate the movements of the surgical instruments rather than directly holding and moving the tools. In such a system, the surgeon is provided with an image of the patient's body at the remote location. A viewing instrument, typically including a miniaturized video camera, is inserted into the body part through a small surgical opening and a variety of surgical instruments and retractors can be inserted through others. The image provided by the viewing device may be displayed on a video screen or television monitor, affording the surgeon enhanced visual control over the instruments. While viewing the three-dimensional image, the surgeon performs the surgical procedures on the patient by manipulating a master device that controls the motion of a servomechanism-actuated instrument. The surgeon's hands and the master device are positioned relative to the image of the operation site in the same orientation as the instrument is positioned relative to the act. During the operation, the instrument provides mechanical actuation and control of a variety of surgical instruments, such as tissue graspers, needle drivers, etc., that each perform various functions for the surgeon, i.e., holding or driving a needle, grasping a blood vessel or dissecting tissue. An overview of the state of the art with respect to robotic surgery technology can be found in "Computer Integrated Surgery: Technology And Clinical Applications" (MIT Press, 1996). Moreover, systems for telesurgery are described in U.S. Pat. Nos. 5,417,210, 5,402,801, 5,397,323, 5,445,166, 5,279,309, 5,299,288.
The robotic system may also be more highly automated. The imaging device may be a computerized tomography (CT) axial imaging system, a magnetic resonance imaging (MRI) device, or any suitable imaging system that provides information regarding the structure of the bodily location to be operated on. The robotic arm is utilized to precisely orient the surgical tools or other implements used in conducting the surgery or related procedure and a control means, such as a computer, utilizes information received from the imaging device, alone or together with other information, to control the robotic arm. Such image-assisted robotic surgery is described in U.S. Pat. No. 5,078,140.
The instruments used in such limited spaces, such as an instrument that could be used to stabilize a treatment site, are necessarily designed for ease of insertion through a small opening and for remote manipulation. Thus, there is a need in the art for new and better devices and methods of using them to stabilizing a surgical site, such as the surface of the beating heart, or for stabilizing a an interior therapeutic or diagnostic treatment site during minimally invasive or robotic surgery.